This invention relates to methods of and compositions for defoliating plants and/or for decreasing regrowth. More particularly, the invention relates to methods of defoliating plants and/or decreasing growth comprising applying to plants a guanidine compound. The invention also relates to compositions comprising a guanidine compound.
Methods of controlled defoliation of plants and inhibition of regrowth after defoliation have important agricultural uses. For example, cotton defoliation prior to harvest eliminates the main source of stain and trash, resulting in better grade cotton. Stain from poorly defoliated plants or regrowth and moisture from green tissue can result in loss of cotton quality. It is desirable that growth of new leaves, referred to as regrowth, be inhibited after defoliation
Examples of compounds that are commonly used as cotton defoliants include S,S,S-tributyl phosphorotrithioate, also known as tributifos and available under the trade name Def-6(copyright), 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea, also known as thidiazuron and available under the trade name Dropp(copyright), dimethiphin and sodium chlorate. Unfortunately, many commonly used cotton defoliants require high application levels. Further, it is desirable that dead leaves drop off the cotton plant, however, in many instances the application of commonly used cotton defoliants results in leaves which are dead but not dropped from the plants.
Thidiazuron provides regrowth control as will as some defoliation. However, in order to attain a suitable level of defoliation tributifos, which causes defoliation but has little regrowth control, is usually applied along with the thidiazuron. It would be convenient if growers could apply a single active ingredient to plants, particularly cotton, which would provide both defoliation and regrowth control.
Speltz et al., U.S. Pat. Nos. 4,594,092, 4,804,780, and 4,944,788, teach guanidine compounds represented by the formula 
wherein X1 is COCH3, halogen, CN, CH2 CN, C(OH)2 CF3, OCHF2, OCF3, CH3, CF3, NO2, OCF2CHF2, OCH3, N(CH3)2, or CH2 OR3 where R3 is H or CH3; Y1 is H, halogen, CH3; Z1 is H, CH3, halogen, OCH3 or CF3; R is H or CH3; with the provisos that when X1 is CH3, OCH3, F, Cl or Br and R is H, then Y1 and Z1 cannot both be hydrogen; and when X1 is Cl and Z1 and R are each hydrogen, then Y1 cannot be methyl; and the salts or tautomers thereof; 
wherein X2 is H, OH, straight or branched C1-C4 alkoxy, halogen, OCF3, CF3, straight or branched C1-C4 alkyl or Y2 is H or F; Z2 is F, H, CH3 or OCH3; W2 is H or F; m is an integer of 0, 1, or 2; R2 is H, CH3, C2 H5 or CF3; with the provisos that when m is 0 and R2 is CH3, then W2, X2, Y2 and Z2 cannot all be hydrogen; and when m is 1, then R2, W2, X2, Y2 and Z2 cannot all be hydrogen; and the salts or tautomers thereof; 
wherein W4 is H or F and X4 is straight or branched C1-C4 alkoxy, straight or branched C1-C4 alkyl or F; with the provisos that when W4 is F, X4 is H; and the salts or tautomers thereof. Speltz et al. teach the use of the compounds for inducing a cytokinin-like response in ornamental and crop plants and for increasing crop yield.
Arotin et al., U.S. Pat. Nos. 4,639,268 and 5,175,365, disclose substituted nitroguanidine or cyanoguanidine compounds of the structure: 
wherein R1 is NO2 or CN; R2 is n-C3H7, CH2OCH3 or CH2CHxe2x95x90CH2; X is hydrogen, o-F, m-F, p-F, m-OCH3, m-OH or p-cl; the salts, tautomers and optical isomers thereof and the (+) or (xe2x80x94)-isomers of compounds having the above structure, wherein R1 and X are as described and R2 is CH3, C2H5 or CF3, for use in preemergence control of undesirable broadleaf weeds and grass plants and in defoliating and/or desiccating plants. Arotin et al. teach that the substituted nitroguanidine or cyanoguanidine compounds may be used in combination with defoliants including N-(substituted phenyl)-N-1,2,3-thiadiazole-5-yl ureas; tributyl phosphorotrithioate; sodium chlorate; 2-(2-imidazolin-2-yl)quinolines; 2-(2-imidazolin-2-yl)-pyridines; O,O,Oxe2x80x2,Oxe2x80x2-tetraethyl dithiopyrophosphate; and 2,1,3-benzothiadiazole-dicarbonitriles.
There is a need for defoliant compositions which can be used at low application levels. There is also a need for methods of inhibiting regrowth of plants, particularly regrowth of cotton leaves, after defoliation.
Accordingly, it is an object of the present invention to obviate problems of the prior art.
It is a further object of the present invention to provide methods of defoliating and/or inhibiting regrowth in plants.
It is a another object of the present invention to provide methods of defoliating and/or inhibiting regrowth in plants which can utilize low application levels of active ingredients.
It is a yet another object of the present invention to provide compositions for defoliating and/or inhibiting regrowth in plants, particularly cotton plants.
It is a further object of the present invention to provide methods of removing a source of stain and trash from cotton.
According to one aspect of the invention there are provided methods of defoliating plants comprising applying to plants an effective amount of a first active ingredient selected from the group consisting of substituted nitroguanidine and cyanoguanidine compounds of the formula: 
wherein R1 is NO2 or CN; R2 is CH3, C2 H5, CF3, n-C3 H7, CH2 OCH3 or CH2CHxe2x95x90CH2; X is hydrogen, o-F, m-F, p-F, m-OCH3, m-OH or p-Cl; and the salts, tautomers and optical isomers thereof; an effective amount of a second active ingredient selected from the group consisting of thidiazuron, diuron, ethephon, protoporphyrinogen oxidase (PPO) inhibitor herbicides; and, optionally, an adjuvant. The weight ratio of the first active ingredient to the second active ingredient is from about 1:0.05 to about 1:200.
According to a further aspect of the invention there are provided methods of inhibiting leaf regrowth in cotton comprising applying to cotton an effective amount of a guanidine compound having the formula (I): 
wherein R1 is NO2 or CN; R2 is CH3, C2 H5 or CF3; and X is hydrogen, o-F, m-F, p-F, m-OCH3, m-OH or p-Cl, and the salts, tautomers and optical isomers thereof.
According to another aspect of the invention there are provided methods of inhibiting leaf regrowth in cotton comprising applying to cotton an effective amount of a first active ingredient selected from the group consisting of (+)isomers and (xe2x88x92)-isomers of guanidine compounds having the formula (I): 
wherein R1 is NO2 or CN; R2 is CH3, C2 H5 or CF3; and X is hydrogen, o-F, m-F, p-F, m-OCH3, m-OH or p-Cl; an effective amount of a second active ingredient selected from the group consisting of thidiazuron, diuron, ethephon, protoporphyrinogen oxidase (PPO) inhibitor herbicides; and, optionally, an adjuvant.
According to further aspects of the invention there are provided compositions comprising 1-(xcex1-ethylbenzyl)-3-nitroguanidine and thidiazuron and compositions comprising (+)-1-(xcex1-ethylbenzyl)-3-nitroguanidine and thidiazuron.
According to yet another aspect of the invention there are provided compositions comprising a first ingredient selected from the group consisting of substituted nitroguanidine and cyanoguanidine compounds of the formula (1): 
wherein R1 is NO2 or CN; R2 is CH3, C2 H5, CF3, n-C3 H7, CH2 OCH3 or CH2CHxe2x95x90CH2; X is hydrogen, o-F, m-F, p-F, m-OCH3, m-OH or p-Cl; and the salts, tautomers and optical isomers thereof; and a second ingredient selected from the group consisting of herbicides, adjuvants, plant growth regulators, desiccants, boll opening compounds, pesticides, fertilizers and defoliants other than guanidine compounds having the formula (I). The second ingredient is present in an amount sufficient to enhance the defoliation and/or regrowth control activity of the first ingredient.
The methods and compositions of the invention of the invention are advantageous in that low levels of the guanidine compounds are required.
These and additional aspects, objects and advantages of the invention are more fully described in the following detailed description.